The present invention relates to an imaging and recording apparatus for electrically recording optical images of a subject as image information signals, and in particular to an imaging and recording apparatus having enhanced manipulation performance when the apparatus is connected to a peripheral device and the image information signals are exchanged between the apparatus and the device.
As conventional apparatuses of this kind, there are so-called electronic cameras. Examples of the electronic cameras include a digital still camera described in Sasaki et al., "Picture coding for digital still camera", Journal of The Institute of Television Engineers of Japan, Vol. 46, No. 3, (1992), pp. 300-307 (hereafter referred to as conventional technique reference 1) and a camera of DS-100 type described in a catalog "FUJIX DIGITAL STILL CAMERA SYSTEM" published by Fuji Photo Film Co. Ltd. in September 1991 (hereafter referred to as conventional technique reference 2).
In electronic cameras described in the conventional technique references 1 and 2, image information signals derived by using an imaging device are digitized (quantized) and recorded in a card having a semiconductor memory thereon (hereafter referred to as memory card) as shown, for example, in FIG. 1 of the conventional technique reference 1.
In the conventional technique references 1 and 2, image information signals are thus handled as digital signals. Therefore, connection to peripheral devices such as personal computers originally handling only digital signals is easy (because signals can be transmitted and received as digital signals without the intervention of analog-digital converters and the like). Furthermore, the image quality degradation is not caused by the transmission line. Thus, the performance of connection with other systems is shown to be good.
In the conventional technique reference 1, concrete examples regarding the connection with peripheral devices are not described. However, it is considered that a memory card is used as an intermediate medium. In the conventional technique reference 2, an example of use of such a memory card is disclosed. That is to say, a memory card is first mounted on an electronic camera to record image information signals. Thereafter, this memory card is detached from the electronic camera and mounted on a peripheral device separate from the electronic camera. The image information signals recorded on the memory card are read out into this peripheral device. In this case as well, no methods are disclosed except the above described method using a memory card as the intermediate medium as the method for transmitting image information recorded in the memory by the electronic camera to the peripheral device in the form of digital signals as they are (with the intervention of neither a digital-analog converter nor an analog-digital converter).
As a known apparatus connected to a personal computer or the like to electrically transmit and receive image information signals, there is a still image compressing and expanding substrate of FSA 2001 type described in "Summary of FSA 2001" published by Fuji Film Microdevices Corporation on Jun. 24, 1991 (hereafter referred to as conventional technique reference 3). The apparatus described in this conventional technique reference 3 incorporates a semiconductor memory for storing digital image information signals. Between this apparatus and a personal computer connected thereto via a connector, a cable and the like, the digital image information signals are stored in the above described semiconductor memory or digital image information signals already stored are transmitted and received in the form of digital signals as they are.
Apparatuses of the conventional technique references 1 and 2 are camera apparatuses having imaging means for generating electrical image information signals from optical images. On the other hand, the apparatus of the conventional technique reference 3 has no such means and image information signals are generated by a personal computer. Image information signals generated by the personal computer are transmitted to the apparatus described in the conventional technique reference and stored temporarily in a first memory. Subsequently, the image information signals read out from the first memory are subjected to image data compression processing using the DCT (discrete cosine transform) method and resultant signals are sent back to the above described personal computer. Such an operation is similar to the operation of the apparatus block shown in FIG. 2 of the conventional technique reference 1.
Operation for writing or reading image information signals in the apparatus described in the conventional technique reference 3 is executed under time management of the connected personal computer. Otherwise, duplication of writing operation and reading operation of information data in the above described first memory may cause data of a certain image to be switched to data of a different image while the former cited data are being read out, resulting in deformed image information. Such a disadvantage can be prevented in the apparatus described in the conventional technique reference 3.
The apparatus described in the conventional technique reference 3 conducts processing for compressing the above described image data and outputs image information signals thus compressed. Data are outputted from this apparatus to the personal computer in synchronism with a clock outputted from the personal computer. However, image data compression is conducted by using an independent clock within this apparatus, i.e., a clock which is not in synchronism with the clock outputted from the personal computer. Therefore, the apparatus has a buffer memory of so-called FIFO (Fast In/Fast out) type.
Operation of this FIFO memory will now be described by referring to FIG. 2.
In FIG. 2, the FIFO memory 21 has data storage areas of memory address 0, 1, 2, . . . , n, n+1, . . . , m. Upon operation start of the memory 21, data are written into address 0, and then in the order of address 1, 2,
The write address is updated every repetition timing of the above described clock within the apparatus. If data are written into the address n, data readout is started from the address 0 at this timing. In the same way as writing, data are then read in the order of address 1, 2, . . . . . The read address is updated every repetition timing of an external clock supplied from the above described personal computer to the above described apparatus. Thereafter, the read address is also updated so as to follow the write address successively updated. As for both writing and reading, upon reaching address m, the address is so controlled as to return to address 0 at the next clock timing.
The FIFO memory is operated as heretofore described. It is now assumed that Aos (=n) is the address offset value of the initial state between writing and reading, whereas A'os (=m-n) is the address offset value between writing and reading when the write address has reached the final address m of the buffer memory, and T is the repetition period of the above described read clock supplied from the outside. Even if the timing of the write clock is deviated from the generation timing of the read clock by at most Aos.times.T in the lag direction and by at most A'os.times.T in the lead direction, data can be read out correctly in the order in which they have been written into the memory. That is to say, between systems activated by asynchronous clocks, data transfer can be executed in the correct order by providing a FIFO buffer memory between them.
In case a FIFO memory is used, however, the write clock (internal clock of the above described apparatus in case of compressed data output operation mode of the apparatus described in the conventional technique reference 3) and the read clock (the clock supplied from the personal computer to the above described apparatus in case of the compressed data output operation mode) cannot be established without mutual relation at all. As for the difference in repetition frequency between clocks, for example, the address offset value regulated from the capacity of the buffer memory in use becomes a restriction factor. Furthermore, the start timing of read operation must be subjected to time management with respect to timing of write operation.
The apparatus described in the conventional technique reference 3 further has a function of inputting a compressed image information signal from the personal computer, restoring the original uncompressed image information signal in an internal data expansion circuit, storing the restored original uncompressed image information signal in the above described first semiconductor memory, and thereafter returning this restored image information signal to the personal computer. In such operation as well, operation timing of this apparatus is executed under management of the connected personal computer. Therefore, it is possible to prevent such a situation that writing, into the first semiconductor memory, an image information signal which has not been subjected to compression processing and which is supplied from the computer overlaps in time with writing the above described restored image information signal into the first semiconductor memory.
In such operation, the FIFO memory operates by using, as a write clock, the clock supplied from the personal computer and using, as a read clock, the internal clock of the apparatus. The interrelation between these two clocks is the same as that of the output operation of the above described compressed image information signal.
In the apparatus described in the conventional technique reference 3, the program of the personal computer connected for use is configured so as to prevent occurrence, in the FIFO memory, of such an operation mode that writing using the internal clock of the apparatus overlaps in time with writing using the clock supplied from the personal computer.
Electronic circuits for the imaging and recording apparatuses such as electronic cameras described in the conventional technique references 1 and 2 can be implemented in extremely small-sized circuit blocks by using recent high-integration LSI technique and high-density substrate mounting technique. Therefore, especially in fabricating a small-sized camera using a monofocus optical lens and a memory card as described in the above described conventional technique reference, the space for housing this memory card, the space for mounting a memory card loading connector, or the space of a mechanism for pulling out the memory card becomes a primary factor hindering the size reduction.
Furthermore, it is conceivable to reduce the size of the memory card as the size of the apparatus is reduced. However, pulling out a further smaller-sized memory card from a smaller-sized apparatus involves troublesome manipulation. There is also a fear that the apparatus will be inadvertently dropped in pulling out the memory card and the apparatus will be destroyed.
The above described disadvantage caused by pulling out and putting in the memory card can be dissolved by providing a connector for inputting and outputting image information signals in the imaging and recording apparatus and thereby sending/receiving signals directly to/from an external device via this connector. In the imaging and recording apparatus, however, there is provided a recording switch corresponding to the shutter button of a conventional film camera. There is a case where closing this recording switch causes execution of operation of taking in an optical image at an arbitrary timing which is desired by the operator and which is not restricted by the operation situation of an external device connected to the above described connector and recording the optical image in the semiconductor memory as an electric signal. Or there is a case where the execution is desired. For example, the case where an external device is put into the connector in such a state that the recording operation within the apparatus is not yet been completed after the recording switch has been closed corresponds to the former case. The case where a picture is to be recorded without throwing away the chance of clicking the shutter at certain moment corresponds to the latter case. In case a connector as described above is provided in the imaging and recording apparatus, there is needed new operation management differing from the aforementioned apparatus described in the conventional technique reference 3, in which every apparatus operation is subjected to centralized management by a computer, in order to prevent deformation of image contents caused by overlap of information writing with information reading in the semiconductor memory or in order to avoid disadvantage of deformation of image contents resulting from competition in the same semiconductor memory between information writing caused by manipulation of the recording switch and information writing inputted from an external device.
Furthermore, a personal computer is conceivable as an external device for exchanging image information with the imaging and recording apparatus. In this case, however, it is extremely effective from the aspects of universality and manipulation capability to make possible information exchange by inputting an information transmission clock having no correlation at all with respect to the system operation clock used within the imaging and recording apparatus from the personal computer to the imaging and recording apparatus.